The military carried out the dumping from 1946 to 1970 — including off the Pacific, Atlantic and Hawaii coasts — so it's no secret. But now that some of the containers used to store the munitions are more than 60 years old, the researchers say it's time to see them as a threat.

"The bottom line is that these bombs are a threat today and no one knows how to deal with the situation," Texas A&M oceanographer William Bryant said in a statement ahead of a briefing he'll give at a weapons disposal conference. "If chemical agents are leaking from some of them, that’s a real problem. If many of them are still capable of exploding, that’s another big problem."

Photos taken during surveys show that some of the chemical weapons canisters, such as those that carried mustard gas, appear to be leaking materials and are damaged, Bryant and others on his team reported.

The surveys have turned up 10 dump sites at 60 and 100 miles out — and one of them had a pipeline running through it.

Texas has the closest dump, followed by Louisiana, "not far from where the Mississippi River delta area is," Bryant said. "Some shrimpers have recovered bombs and drums of mustard gas in their fishing nets.

Texas A&M University

Texas A&M University researchers found this unexploded, 500-pound bomb at a dumpsite near the mouth of the Mississippi River in 2008.

"No one seems to know where all of them are and what condition they are in today," he added. "The best guess is that at least 31 million pounds of bombs were dumped, but that could be a very conservative estimate.

"These were all kinds of bombs, from land mines to the standard military bombs, also several types of chemical weapons," he said. "Our military also dumped bombs offshore that they got from Nazi Germany right after World War II.

"Is there an environmental risk? We don’t know, and that in itself is reason to worry," he said.

The hazards pose even more of a risk as the Obama administration and energy companies pick up the pace of drilling after the 2010 BP oil spill.

Ironically, unexploded ordnance was found in the offshore zone known as Mississippi Canyon where the BP well was drilled.

Pentagon

This chart lists some of the munitions dumpsites in the Gulf of Mexico, and what's there.

"My first thought when I saw the news reports of the Deepwater Horizon explosion in the Gulf two years ago were, 'Oh my gosh, I wonder if some of the bombs down there are to blame'," recalled Bryant.

That turned out not to be the case, but such World War II finds are not surprising in the oil industry.

Last year, BP shut a major North Sea pipeline for five days to remove a 13-foot unexploded German mine. BP discovered the mine during an inspection, then spent months devising a plan to remove and safely detonate it.

Pentagon

This chart lists some of the munitions dump sites in the Gulf of Mexico, and what is there.

In 2001, BP and Shell found the wreckage of the U-166, a German WWII submarine, 45 miles from the mouth of the Mississippi River.

While the practice of dumping bombs and chemical weapons in the ocean ended 40 years ago, some effects are just now being seen, Terrance Long, founder of the International Dialogue on Underwater Munitions, told Reuters. Bryant will be briefing the group's conference, which begins Monday in San Juan, Puerto Rico.

"You can find munitions in basically every ocean around the world, every major sea, lake and river," Long said. "They are a threat to human health and the environment."